1. Field
Embodiments relate to a nonvolatile semiconductor memory device.
2. Description of the Related Art
A NAND type flash memory is known as a nonvolatile semiconductor memory device that is electrically rewritable and capable of a high degree of integration. A memory cell of the NAND type flash memory includes: a charge accumulation layer formed on a semiconductor substrate via a tunnel insulating film; and a control gate stacked on the charge accumulation layer via an inter-gate insulating film. The memory cell stores data in a nonvolatile manner by a charge accumulation state of the charge accumulation layer.
This NAND type flash memory, after performing a write operation to the memory cell, executes a write verify operation that verifies whether desired data has been written in the memory cell. When the write operation and the write verify operation are performed sequentially on a plurality of the memory cells, there is a risk that operation conditions change between the write verify operation on a first half of the memory cells and the write verify operation on a second half of the memory cells, whereby the write verify operation cannot be precisely executed.